with occasional P 0445 assisting... I thought that to address "a massive leak" in the evaporative system would be easier than to chase elusive P0170. I did not find any broken hose connecting canisters. but I did not succeed in removing the purge valve. Two molded tubes are connecting it to steel tubes by the some strange contraption that refused to cooperate. I was squeezing it, pushing, pulling and twisting, but in vain. Do I need some special tool to do it?
I finally got more sofisticated data reader than just a plain code reader.
Live data not encouraging : shortFT1 -3.1
shortFT2 -3.9
long FT1 19.5
longFT 2 0.6
at idle speed.

at 2000RPM sFT1 15.6
sFT2 -2.3
lFT1 10.9
lFT2 5.5

it seems to indicate the right bank has an air leak, but I cannot find it. Spraying carb cleaner around manifold did not change idle speed. The motor runs smoothly, accelerates ok, but as I stated previously every once a while it goes to "restricted performance" mode for a few minutes before recovering to its normal regime. Any advice appreciated. I am out of my wits.

 

19.5 is the maximum LTFT, so that is probably the reason for the code.

A small leak probably won't change idle speed when you hit it with carb cleaner, but you should see it show up on the fuel trims. You could try watching the live STFT while spraying around the manifold.